# * George Moschovitis  <gm@navel.gr>
# (c) 2004-2005 Navel, all rights reserved.
# $Id: hierarchical.rb 1 2005-04-11 11:04:30Z gmosx $

require 'glue/dynamic_include'

module Og

# Implements the Nested Sets pattern for hierarchical 
# SQL queries.

module NestedSets

	def self.append_dynamic_features(base, options)
		c = { 
			:left => 'lft', 
			:right => 'rgt', 
			:type => Fixnum, 
			:scope => '"1 = 1"',
			:parent => Inflector.name(base),
			:children => Inflector.plural_name(base)  
		}
		c.update(options) if options

		parent = "#{c[:parent]}_oid"
		left = c[:left]
		right = c[:right]
		children = c[:children]
		child = Inflector.singularize(children)

	 	if c[:scope].is_a?(Symbol) && c[:scope].to_s !~ /_oid$/
			c[:scope] = "#{c[:scope]}_oid".intern
		end
		scope = c[:scope]
		if scope.is_a?(Symbol)
			scope = %{(#{scope} ? "#{scope} = \#{@#{scope}}" : "#{scope} IS NULL")}
		end
		
		base.module_eval <<-EOE, __FILE__, __LINE__		
			property :#{parent}, Fixnum, :sql_index => true
			property :#{left}, :#{right}, #{c[:type]}

			def root?
				(@#{parent}.nil? || @#{parent} == 0) && (@#{left} == 1) && (@#{right} > @#{left})			
			end
		
			def child?
				(@#{parent} &&  @#{parent} != 0) && (@#{left} > 1) && (@#{right} > @#{left})			
			end
                                   
			def #{children}_count
				return (@#{right} - @#{left} - 1)/2
			end

			def full_#{children}(extrasql = nil)
				#{base}.all("WHERE " + #{scope} + " AND (#{left} BETWEEN \#\{@#{left}\} AND \#{@#{right}}) \#{extrasql}")
			end

			def #{children}(extrasql = nil)
				#{base}.all("WHERE " + #{scope} + " AND (#{left} > \#\{@#{left}\}) AND (#{right} < \#{@#{right}}) \#{extrasql}")
			end
														
			def direct_#{children}(extrasql = nil)
				#{base}.all("WHERE " + #{scope} + " AND #{parent} = \#{@oid} \#{extrasql}")
			end

			def add_#{child}(child)
				self.reload if @oid
				child.reload if child.oid
				
				if @#{left}.nil? || @#{left} == 0 || @#{right}.nil? || @#{right} == 0
					@#{left} = 1
					@#{right} = 2 
				end
			
				child.#{parent} = @oid
				child.#{left} = pivot = @#{right}
				child.#{right} = pivot + 1
				@#{right} = pivot + 2

				self.class.transaction do
					self.class.update("#{left} = (#{left} + 2)",  "WHERE " + #{scope} + " AND #{left} >= \#{pivot}")
					self.class.update("#{right} = (#{right} + 2)",  "WHERE " + #{scope} + " AND #{right} >= \#{pivot}")
				end
			
				self.save
				child.save
			end
			
			def self.og_pre_delete(conn, obj)
				return unless (obj.#{left} and obj.#{right})

				span = obj.#{right} - obj.#{left} + 1
				
				(klass = obj.class).transaction do 
					klass.delete(#{scope} + " AND #{left} > \#{obj.#{left}} AND (#{right} < \#{obj.#{right}})")
					klass.update("#{left} = (#{left} - \#{span})",  "WHERE " + #{scope} + " AND #{left} >= \#{obj.#{right}}")
					klass.update("#{right} = (#{right} - \#{span})",  "WHERE " + #{scope} + " AND #{right} >= \#{obj.#{right}}")
				end
			end
		EOE
	end

end

# Transform the base class to a hierarchical node.
# A selection of different implementation strategies
# are provided.
#
# === Example
#
# class Comment
#		include Hierarchical, :method => :nested_sets
# end
#
# [+:method+]
# 	:simple
# 	:nested_sets
# 	:nested_intervals

module Hierarchical

	def self.append_dynamic_features(base, options)
		c = { 
			:method => :nested_sets, 
		}
		c.update(options) if options

		base.include(NestedSets)
	end

end

end